Backpack



FIG. 1 is a front perspective view of the backpack showing my new design;

FIG. 2 is a back view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof; and,

FIG. 6 is a top view thereof.

The broken lines on the bottom of the backpack depict environmental subject matter that forms no part of the claimed design. The remaining broken lines depict stitching and portions of the backpack that form no part of the claimed design. 

CLAIM The ornamental design for a backpack, as shown and described. 